Ionothermal Synthesis, Crystal Structure, and Magnetic Study of Co2PO4OH Isostructural with Caminite

A new framework cobalt(II) hydroxyl phosphate, Co2PO4OH, was prepared by ionothermal synthesis using 1-butyl-4-methyl-pyridinium hexafluorophosphate as the ionic liquid. As the formation of Co2PO4F competes in the synthesis, the synthesis conditions have to be judiciously chosen to obtain well-crystallized, single phase Co2PO4OH. Single-crystal X-ray diffraction analyses reveal Co2PO4OH crystallizes with space group I41/amd (a = b = 5.2713(7) Å, c = 12.907(3) Å, V = 358.63(10) Å3, and Z = 4). Astonishingly, it does not crystallize isotypically with Co2PO4F but rather isotypically with the hydroxyl minerals caminite Mg1.33[SO4(OH)0.66(H2O)0.33] and lipscombite Fe2–yPO4(OH) (0 ≤ y ≤ 2/3). Phosphate tetrahedra groups interconnect four rod-packed face-sharing ∞1{CoO6/2} octahedra chains to form a three-dimensional framework structure. The compound Co2PO4OH was further characterized by powder X-ray diffraction, Fourier transform–infrared, and ultraviolet–visible spectroscopy, confirming the discussed structure. The magnetic measurement reveals that Co2PO4OH undergoes a magnetic transition and presents at low temperatures a canted antiferromagnetic spin order in the ground state

Phosphonium Chloromercurate Room Temperature Ionic Liquids of Variable Composition

The system trihexyl(tetradecyl)phosphonium ([P66614]Cl)/mercury chloride (HgCl2) has been investigated by varying the stoichiometric ratios from 4:1 to 1:2 (25, 50, 75, 100, 150, and 200 mol % HgCl2). All investigated compositions turn out to give rise to ionic liquids (ILs) at room temperature. The prepared ionic liquids offer the possibility to study the structurally and compositionally versatile chloromercurates in a liquid state at low temperatures in the absence of solvents. [P66614]2[HgCl4] is a simple IL with one discrete type of anion, while [P66614]{HgCl3} (with {} indicating a polynuclear arrangement) is an ionic liquid with a variety of polyanionic species, with [Hg2Cl6]2– apparently being the predominant building block. [P66614]2[Hg3Cl8] and [P66614][Hg2Cl5] appear to be ILs at ambient conditions but lose HgCl2 when heated in a vacuum. For the liquids with the compositions 4:1 and 4:3, more than two discrete ions can be evidenced, namely, [P66614]+, [HgCl4]2–, and Cl– and [P66614]+, [HgCl4]2–, and the polynuclear {HgCl3}−, respectively. The different stoichiometric compositions were characterized by 199Hg NMR, Raman- and UV–vis spectroscopy, and cyclic voltammetry, among other techniques, and their densities and viscosities were determined. The [P66614]Cl/HgCl2 system shows similarities to the well-known chloroaluminate ILs (e.g., decrease in viscosity with increasing metal content after addition of more than 0.5 mol of HgCl2/mol [P66614]Cl, increasing density with increasing metal content, and the likely formation of polynuclear/polymeric/polyanionic species) but offer the advantage that they are air and water stable

Rare earth metal-containing ionic liquids

As an innovative tool, ionic liquids (ILs) are widely employed as an alternative, smart, reaction media (vs. traditional solvents) offering interesting technology solutions for dissolving, processing and recycling of metal-containing materials. The costly mining and refining of rare earths (RE), combined with increasing demand for high-tech and energy-related applications around the world, urgently requires effective approaches to improve the efficiency of rare earth separation and recovery. In this context, ionic liquids appear as an attractive technology solution. This review addresses the structural and coordination chemistry of ionic liquids comprising rare earth metals with the aim to add to understanding prospects of ionic liquids in the chemistry of rare earths

Unusual Electronic and Bonding Properties of the Zintl Phase Ca5Ge3 and Related Compounds. A Theoretical Analysis

Theoretical reasons for metallic behavior among diverse Zintl phases have generally not been pursued at an advanced level. Here, the electronic structure of Ca5Ge3 (Cr5B3 type), which can be formulated (Ca+2)5(Ge2-6)Ge-4 in oxidation states, has been explored comparatively by means of semiempirical and first-principles density functional methods. The FP-APW calculations show that alkaline-earth-metal and germanium orbitals, particularly the d orbitals on the cations and the p-π* orbitals of the halogen-like dimeric Ge2-6, mix considerably to form a conduction band. This covalency perfectly explains the unusual metallic properties of the nominally electron-precise Zintl phase Ca5Ge3 and its numerous relatives. Similar calculational results are obtained for Sr5Ge3, Ba5Ge3, and Ca5Sn3. Cation d orbitals appear to be a common theme among Zintl phases that are also metallic

Solution-Based Synthesis of GeTe Octahedra at Low Temperature

GeTe octahedra were prepared by reaction of equimolar amounts of GeCl2·dioxane and Te(SiEt3)2 in oleylamine, whereas a slight excess of the Te precursor yielded GeTe octahedra decorated with elemental Te nanowires, which can be removed by washing with TOP. The mechanism of the GeTe formation is strongly influenced by the solvent. The expected elimination of Et3SiCl (dehalosilylation) only occurred in aprotic solvents, whereas Te(SiEt3)2 was found to react with primary and secondary amines with formation of silylamines. Temperature-dependent studies on the reaction in oleylamine showed that crystalline GeTe particles are formed at temperatures higher than 140 °C. XRD, SAED, and HRTEM studies proved the formation of rhombohedral GeTe nanoparticles. These findings were confirmed by a single-crystal and powder X-ray analysis. The rhombohedral structure modification was found, and the structure was solved in the acentric space group R3m

Valence Compounds versus Metals. Synthesis, Characterization, and Electronic Structures of Cubic Ae4Pn3 Phases in the Systems Ae = Ca, Sr, Ba, Eu; Pn = As, Sb, Bi

The isostructural compounds Sr4Bi3, Ba4Bi3, and Ba4As∼2.60 were prepared by direct reactions of the corresponding elements and their structures determined from single-crystal X-ray diffraction data as anti-Th3P4 type in the cubic space group I4̄3d, Z = 4 (a = 10.101(1) Å, 10.550(1) Å, 9.973 (1) Å, respectively). The two bismuth compounds are stoichiometric, and the arsenide refines as Ba4As2.60(2). Only unrelated phases are obtained for all binary combinations among the title components for either Ca or Sb. The magnetic susceptibility and resistivities of Ba4Bi3 and Eu4Bi3 show that they are good metallic conductors (∼40 μΩ·cm at 298 K), whereas Ba4As2.60 exhibits ρ150 \u3e 1000 μΩ·cm. The electronic structures of Sr4Bi3, Ba4Bi3, and Ba4As3 were calculated by TB-LMTO-ASA methods. Mixing of cation d states into somewhat disperse valence p bands on Bi results in empty bands at EF and metallic behavior, whereas the narrower valence band in the electron-deficient Ba4As3 leads to vacancies in about 11% of the anion sites and a valence compound

Nine Hexagonal Ca5Pb3Z Phases in Stuffed Mn5Si3-Type Structures with Transition Metal Interstitial Atoms Z. Problems with Classical Valence States in Possible Zintl Phases

Ternary hexagonal Ae5Tt3Z phases have been obtained from high-temperature reactions (1000−1300 °C in Ta) only for Ae (alkaline-earth metal) = Ca, Tt (tetrel) = Pb, and Z = V, Cr, Mn, Fe, Co, Ni, Zn, Ru, or Cd. The hexagonal crystal structures (stuffed Mn5Si3-type, P63/mcm, Z = 2) were refined for Z = Mn and Fe (a = 9.3580(3), 9.3554(5) Å, c = 7.009(1), 7.009(1) Å, respectively). In contrast, Ca5Pb3Z for Z = Cu or Ag form only with a trigonal structure (P3̄c1, Z = 2, a = 9.4130(3) Å, c = 7.052(1) Å for Cu) in which regular displacements of only the linear strings of Ca1 atoms occur. The existence of these compounds stands in contrast to the nonexistence of all binary Ae5Tt3 products from Ca to Ba (Ae) and Si to Pb (Tt) with a Mn5Si3-type structure. Therefore, it once seemed attractive to consider the Z elements in these Ca5Pb3Z compounds as reducing agents (electron donors). The Mn and Fe structures appropriately exhibit greatly enlarged antiprismatic calcium cavities about Z. Other indications of relatively electron-poor environments around Fe are found in its properties, which include soft ferromagnetism with an elevated magnetic moment (6.3 μB) and a large Fe 3p3/2 binding energy relative to that in La5Ge3Fe, La15Ge9Fe, etc. The Ca5Pb3Mn phase exhibits metallic behavior (ρ295 = 135 μΩ cm) and temperature-independent Pauli paramagnetism. These properties are supported by ab initio band structure calculations for Ca5Pb3Mn, which show strong Ca−Pb bonding and a broad Pb-based band, with appreciable Ca−Mn and Ca−Pb bonding states at and above EF. Distortion of the Cu analogue gives strengthened Ca−Pb bonding and reduced Cu−Ca1 repulsions. A Zintl phase description of these compounds and some releated compounds in terms of closed Pb bands is not appropriate